Conventional formwork for forming walls from pourable building material such as concrete consist of two opposed, typically plywood walls connected by a rod, trusswork or other connecting structure. More recently, it has become desirable to use insulating material such as expandable polystyrene for the formwork, in order to provide thermal and acoustic insulation to the finished wall. In certain applications, particularly those where it is desired to inhibit the effects of “thermal inertia” of a concrete wall so as to employ the ability of the concrete to retain heat for temperature stabilization, it is desirable to employ formwork with insulated paneling on only one side. The other side, typically of plywood, may or may not be removed after full or at least partial curing of the concrete.
Various insulated formworks and related technologies have been considered. For example, U.S. Pat. No. 5,845,445 to Blackbeard discloses an insulated concrete form with a plurality of plywood boards at an inside surface, and a plurality of insulating foam panels at an outside surface. The plywood boards and insulating foam panels are connected by a plurality of elongated vertically aligned connecting members for retaining the panels in a spaced apart parallel relationship during the wall building process. The connecting members are connected to the insulating panels, and ties are attached to respective connecting members and the plywood boards. Each tie has a conventional embossed end to engage into a latch clip on the plywood side. During de-forming, the plywood boards may be removed by removing the attachment between the ties and latch clips.
U.S. Pat. No. 6,314,694 to Cooper et al. discloses a one-side insulated formwork that includes an insulating panel connectable to a removable panel by a connecting structure, which may provide permanent reinforcement embedded in the insulating panel. The removable panel is attached to the connecting structure using removable fasteners. The connecting structure maintains a fixed spaced relationship between the insulating panel and the removable panel, and according to embodiments disclosed includes rebar hooks for supporting rebar for embedding in the concrete. After the concrete has at least partially cured, the removable fasteners and removable panel are removed, leaving exposed and flush with the outer surface of the concrete wall a surface of the connecting structure suitable for flush connection of a finishing panel.
U.S. Pat. No. 6,526,713 to Moore, Jr. discloses an insulated concrete structure for forming walls from a pourable building material such as concrete. Moore proposed connecting two panels of a formwork using a web structure, a portion of which is preferably embedded in an insulating one of the panels. After the concrete has at least partially cured, one of the panels being now adjacent to the formed wall, may be removed or remain as part of the structure.
U.S. patent application Ser. No. 11/979,826 entitled “One-Sided Insulated Concrete Form” filed on Nov. 8, 2007 by Victor Amend and incorporated in its entirety herein by reference discloses a tie for connecting and maintaining first and second panels of a concrete formwork in a fixed, spaced relationship during a wall building process.
Although the above references disclose insulated formwork of various configurations, improvements are desired. For example, it has been discovered that in certain circumstances, ties that are made of plastic may pose fire safety concerns. In the event of a fire in a building having plastic ties embedded in concrete, the heat of the fire may cause melting of the plastic ties, thereby undesirably creating a passageway in the concrete wall through which smoke and flames can pass.
Ties that are made of metal better resist deformation due to heat, and therefore in the event of a fire do not generally create such passageways through which smoke and flames can pass. However, metal ties are more difficult than plastic ties to cut and otherwise manipulate in the field during construction of a form. Furthermore, unlike plastic ties, for concrete forms made using polystyrene panels, metal ties being placed in a mold or extrusion equipment for embedding in the polystyrene panel during its formation can tend to scratch and thereby damage the equipment.
It is therefore an object of an aspect of the present invention to provide a novel wall form device for connecting and maintaining a first panel and a second panel of a concrete formwork in a fixed, spaced relationship during a wall building process that addresses the above deficiencies.